The update is not available by searching through the store as it is still in beta but can be downloaded using the link which follows:
This beta version of Facebook for Windows Phone can be installed alongside the regular version for anyone who wants to try it out. However keep in mind that it is not stable and could likely crash. Users who are interested in providing feedback are welcome to try it out. Keep in mind that the app currently only supports English Language,
New features of Facebook for Windows Phone include
- Support for high-resolution photos
- Post sharing
- Facebook Timeline
There is no news on how long the beta program will last. Also keep in mind that it is only available for Windows Phone 8 and Windows Phone 7.x users are continued to be left in the dust.